1. Field of the Invention
The present invention relates to a halogen-free reactive flame-retardant polyester, and more particularly to modified phosphorus-containing unsaturated polyester.
2. Description of the Related Art
It is known that flame retardants are roughly classified into halogen-based flame retardants, silicon-based flame retardants and phosphorus-based flame retardants, among which the halogen-based flame retardants have occupied an important position since the 20th century, because this type of flame retardants has good flame resistance, can be used in a low dosage, causes less impact on the performance of materials, and costs a moderate price. However, since halogen would cause environmental pollution problems, and furthermore, halogen-based flame-retardant polymer may generate a lot of smoke and corrosive gases in thermal cracking and burning, the prospect of the halogen-based flame retardants is cast with a shadow, and more and more users, especially in the electronics/electrical industry, are cautious about the halogen-based flame retardants. In recent years, due to the advantages of little smoke, having no toxicity, involving a small amount of halogen or being free of halogen, the phosphorus-based flame retardants have gradually replaced the halogen-based flame retardants and become an object that is extensively researched and developed in the industry. The compound
and derivatives thereof are a novel type of phosphorus-based flame retardants that have been rapidly developed in recent decades. Due to the special molecular structure, the compounds have better thermal stability and chemical stability than common non-cyclic organophosphates, and further, have the advantages of high carbon content, being free of halogen, little smoke, no toxicity, being non-migratory and persistent flame resistance. For example, US Patent Publication No. 2009/0198011 and Chinese Patent No. 101525420 B both disclose a flame retardant containing an ingredient 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).
However, the compatibility of the flame retardant containing the ingredient DOPO with a non-polar solvent or a radiation-curable material (such as a vinyl material)/monomer (such as styrene) is poor. In practical application (for example, the application in a coating), the problem of compatibility occurs, thus easily resulting in problems such as that the distribution of the coating is not even after curing and the flame retardant material separates out, which make restrictions on the applications of the flame retardant.
Given the above, the present invention provides a modified phosphorus-containing unsaturated polyester that can be easily synthesized and conveniently mass-produced, has a radiation-curable group and has good compatibility with a radiation-curable material (such as a vinyl material)/monomer (such as styrene), and can be cross-linkedly polymerized with the radiation-curable material/monomer. Additionally, since the modified phosphorus-containing unsaturated polyester also exhibits good compatibility with a non-polar solvent, and can further reduce film shrinkage, this flame-retardant polyester has a wider spectrum of applications.